Intelligence chiefs told Alastair Campbell that they could not "improve" the claim that Saddam Hussein "might" be able to deploy weapons of mass destruction in 45 minutes, the Hutton inquiry heard today.

The government's director of communications, giving evidence for the first time on day six of the judicial inquiry into government scientist David Kelly's death, insisted he had not requested that the claim be improved, and had only made the suggestion to the chairman of the joint intelligence committee, John Scarlett.

Taking the witness stand, Mr Campbell was repeatedly forced to dismiss as "office chatter" emails by his own Downing Street staff saying that the government's September 2002 dossier "personalised" Saddam Hussein and used selective quotes from his speeches to portray him as "a bad man".

But a picture emerged of the frantic flurry of activity preceding the publication of the September 24 document with even the foreign secretary's office writing that the document "needs a killer para[graph]".

And Phil Bassett, another Downing Street special adviser, admitted in a September 11 email that there was "a long way to go with this and I think we are in a lot of trouble as we stand now".

That comment, made less than a fortnight before publication of the dossier suggests there was not enough of what Mr Campbell elsewhere calls in his diaries, "revelatory, new and informative" information to satisfy what he called the "political media judgment".

Mr Campbell, appearing more hesitant and defensive than during in his foreign affairs select committee appearance, was forced to read out extracts from his yet unpublished diary to the inquiry to defend his role in the dossier. In one entry, also from September 11, he wrote of the dossier "the drier the better and cut the rhetoric" and that its language was too "colourful".

But under cross-examination from James Dingemans QC for Lord Hutton, Mr Campbell suffered several embarrassing moments.

The most noticeable of these was when an email from Daniel Pruce, a press officer based in Downing Street, was read out saying that the dossier should "personalise" the Iraqi leader as a "bad man".

Mr Campbell insisted that he did not "recall responding to that memo", and that Mr Pruce was "a good press officer but [was] making contributions above his pay grade".

He also said that such comments were "office chatter" and based on earlier drafts of the dossier.

But Mr Campbell did admit that on September 6, he wrote in an email that he had discussed with the foreign secretary the "media-friendly editorial job that will need to be done when Jack Straw and his team have produced the dossier".

The inquiry found another memorandum querying the Downing Street claim that there were 20 tonnes of WMD unaccounted for, calling this suggestion "not wrong but it has a lot of spin on it".

In fact, the document states, there were only 2.5 tonnes declared unaccounted for by Unscom while Iraq had refused to reveal documents relating to a further 15 tonnes.

The inquiry was read a letter from a former senior British official with responsibility for intelligence on Iraq who said he was "recording and explaining my reservations" about the government's claims on Iraqi WMD.

However, this potentially explosive confession came from July 2001, predating the government's first weapons' dossier.

Mr Campbell also revealed that in early September he had offered the writing skills of John Williams - like him a former Daily Mirror political journalist - who now works as a government press officer.

But Mr Scarlett at the JIC had rejected that offer saying he wanted "ownership" of the dossier.

On having his suggestion of John Williams write the dossier rejected, Mr Campbell admitted in another memo "writing by committee does not work but we will make suggestions and recommendations."

One of those came from Jonathan Powell, the PM's chief of staff, on September 17 saying: "In the penultimate paragraph you need to make it clear Saddam could not attack us at the moment."

The inquiry heard that the claim of Iraq's alleged 45 minute WMD capability had been weakened from "could" on September 10 to "may be able to" on September 16.

Mr Scarlett later wrote to Mr Campbell saying: "We cannot improve on 'might' on page 16." Mr Campbell denied having requested an "improvement".